TxDOT RWIS Definitions Page
Air Temperature - temperature of the air measured approximately eight
feet above the ground and measured in degrees Fahrenheit degrees
Barometric Pressure - the amount of downward force exerted by the
weight of the air above us, measured in inches of mercury
The following table generally summarizes wind and barometer indications in
the United States. The amateur forecaster should modify the table in accordance
with his or her own observations. The following show the wind direction,
the barometer reduced to sea level and the character of the weather indicated:
- SW to NW, 30.10 to 30.20 and steady - Fair with slight temperature
change for 1 to 2 days.
- SW to NW, 30.10 to 30.20 and rising rapidly - Fair, followed within
2 days by rain.
- SW to NW, 30.20 and above and stationary - Continued fair, with no
decided temperature change.
- SW to NW, 30.20 and above and falling slowly - Slowly rising temperature
and fair for 2 days.
- S to SE, 30.10 to 30.20 and falling slowly - Rain within 24 hours.
- S to SE, 30.10 to 30.20 and falling rapidly - Wind increasing in force,
with rain within 12 to 24 hours.
- SE to NE, 30.10 to 30.20 and falling slowly - Rain in 12 to 18 hours.
- SE to NE, 30.10 to 30.20 and falling rapidly - Increasing wind, and
rain within 12 hours.
- E to NE, 30.10 and above and falling slowly - In summer, with light
winds, rain may not fall for several days. In winter, rain within 24 hours.
- E to NE, 30.10 and above and falling rapidly - In summer, rain probably
within 12 to 24 hours. In winter, rain or snow, with increasing winds, will
often set in when the barometer begins to fall and the wind sets in from
the NE.
- SE to NE, 30.00 or below and falling slowly - Rain will continue 1
to 2 days. SE to NE, 30.00 or below and falling rapidly - Rain, with high
wind, followed, within 36 hours by clearing, and in winter by colder.
- S to SW, 30.00 or below and rising slowly - Clearing within a few hours,
and fair for several days.
- S to E, 29.80 or below and falling rapidly - Severe storm imminent,
followed within 24 hours, by clearing, and in winter by colder.
- E to N, 29.80 or below and falling rapidly - Severe northeast gale
and heavy precipitation; in winter, heavy snow, followed by a cold wave.
- Going to W, 29.80 or below and rising rapidly - Clearing and colder.
Source: National Weather Service
http://www.usatoday.com/weather/wfbarrow.htm
Precipitation Intensity –the intensity of the precipitation derived
from the precipitation type, and classified as light, moderate, or heavy
by the National Weather Service
Precipitation Rate – average precipitation rate calculated every minute.
For snowfall, the rate represents the rate of the liquid equivalent.
(What measures this?)
Precipitation Accumulation – amount of rainfall, or snowfall equivalent,
from midnight GMT to the current time
Road Temperature – The temperature of the roadway surface measured
in degrees Fahrenheit.
Relative Humidity - percentage of moisture in the air. 0% signifies
no moisture in the atmosphere, and 100% means that the air is completely
saturated and unable to absorb more moisture.
Roadway Water Depth - depth of water layer on the roadway measured
from the curb in feet. Any water level could be dangerous or cause
damage to life and property.
Wind Speed – average speed of the wind during a one-minute period,
and can be measured in both miles per hour (mph) and nautical miles per hour
(nm/h or knots) (Perhaps a photo of the device used for this data collection
would be helpful)Check with Frank or Jennifer about the incriment
Wind Gust – the highest wind speed registered over the previous 10
minutes. If no gusts are detected more than 5 nm/h faster than the
average wind speed, then this field is zero. Check with Jennifer or Frank
about the time increment
Wind Direction – This is the direction from which the wind is blowing,
in degrees from north. Zero is north, increasing degrees in a clockwise
direction: 90 is East, 180 is South, 270 is West, 0 and/or 360 is North.
Watch and Warning Definitions
http://www.crh.noaa.gov/lmk/hydro.htm
Helpful Links
General Forecast Terminology
Terms used in our zone and short term forecast program, including sky cover,
temperature, wind, probability of precipitation, heat index, and wind chill.
Severe Weather Terms
Terms used during severe convective weather, including severe thunderstorms,
tornadoes, and flash floods.
Winter Weather Advisory
Terms
Terms used during winter weather advisory situations, and ALERT the public
of situations that may cause inconvenience or difficulty to travelers, or
for people who must be outdoors.
Winter Weather Warning
Terms
Terms used during winter weather warning situations, and ALERT the public
of situations that may cause inconvenience or difficulty to travelers, or
for people who must be outdoors.
Non-Precipitation Weather Terms
Terms used to describe weather events not related to precipitation, such
as fog and high wind.
Hydrologic Terms
Terms used in our hydrologic program, including river stages and observations,
flooding and flash flooding.
Coastal/Oceanic/Marine Terms
Terms used to describe the marine program (not generally applicable for our
county warning area), including hurricanes and tropical storms.
General Weather Glossary
General weather terminology.
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Texas Department of Transportation
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